Physiological saline solution (about 9 mg/ml=154 mmol/l) is typically used to prime the extra corporeal circuit before a dialysis patient is connected to the dialysis equipment and to rinse back the blood from the extracorporeal circuit after a dialysis treatment. The purpose of priming the circuit is to remove air from the blood lines and the dialyser as well as to remove possible fragments of remaining sterilising agents or other residuals from the disposables elements, such as bloodlines and dialysers that form the extracorporeal circuit, before the patient is connected. Rinse back is performed to avoid loss of patient blood that would otherwise remain in the extracorporeal circuit.
The conventional way of doing this is to use for instance a 2 liters bag of physiological saline solution of which 1.5 liters is used for priming of the circuit and 0.5 liters is used for rinse back of the blood to the patient after the treatment.
Modern dialysis equipment can perform so called on-line treatments, which means that the substitution fluid for hemofiltration or hemodiafiltration is prepared on-line by means of ultrafiltration of dialysis fluid in several steps to obtain a sterile and pyrogen free fluid.
On-line prepared substitution fluid can be prepared in practically unlimited quantities which means that this fluid also can be used for priming, bolus and rinse back purposes which also is cost saving and convenient from a handling point of view.
However, substitution fluid has to contain a high concentration of bicarbonate. Infusing priming liquid with this volume and composition into the patient often causes problems, e.g. not well feeling. This problem is known from “Gambro AK 200 ULTRA™ operator's manual HCEN9568. Rev 12.1999 and cautioned for in all on-line systems Clinics experiencing such problems often go back to priming with saline from bags.
There is therefore a long felt need for a simple, cheap and practical manner of providing a priming solution.